Power delivery to the human heart from a 200MHz low-frequency transmitter (left) and a 1.7GHz high-frequency transmitter (right) (Source: medgadget.com)

This could eliminate large pacemaker batteries that don't last forever

Stanford University engineers have created a tiny, wireless cardiac device that can easily be implanted in the chest.

The Stanford researchers, including study leader Ada Poon and doctoral candidates Sanghoek Kim and John Ho, developed a cardiac implant device that is wirelessly powered by radio waves outside of the body instead of depending on a battery.

What's the problem with batteries? They're large -- often the largest part of a pacemaker device. Also, they don't last forever, so patients must have surgery to replace it when the battery stops working.

The new Stanford cardiac device is only eight-tenths of a millimeter in radius. This makes it non-invasive, and easy to place in the human chest. The device combines radiative and inductive transmission of power, allowing a transmitter to send radio waves to a coil in the body. An electrical current is created in the coil, which powers the tiny implant.

This particular wireless device is beating the odds, because electric fields dissipate in human tissues and scientists long thought that high frequency radio waves needed low-frequency transmitters and huge antennas in order to make implantable devices work. But Poon found another way: radio waves move in alternating waves of magnetic and electric fields, allowing high-frequency signals to penetrate human tissues much deeper.

With a 1.7 GHz high-frequency transmitter, the top power transfer through human tissue was able to hit about 1.7 billion cycles per second. This is 10 times that of current devices.

Challenges still lie ahead; such as problems with tissue heating and antenna placement for maximum efficiency (which could significantly reduce power if aligned incorrectly), but the new device is a promising step toward advanced, wireless pacemakers that are both small and powerful.

..now if someone would make it using simply thermal energy - taking advantage of the fact that the human body is above 30º when alive... then the "transmitter" would be the human body... that would be the ultimate/perfect pacemaker :)

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